of, relating to, or involving the sternum, the clavicle, and the mastoid process.


a thick muscle on each side of the neck, the action of which assists in bending the head and neck forward and sideways.

Origin of sternocleidomastoid

1820–30; sterno- + Greek kleido-, combining form of kleís key, clavicle + mastoid Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Word Origin and History for sternocleidomastoid

from sterno-, comb. form of Greek sternon or Latin sternum (see sternum) + Greek kleis (see clavicle) + mastoid.

Online Etymology Dictionary, © 2010 Douglas Harper

sternocleidomastoid in Medicine




Relating to or characterizing the sternum, the clavicle, and the mastoid process.


A muscle with origin from the anterior surface of the episternum and from the sternal end of the clavicle, with insertion into the mastoid process and the superior nuchal line, with nerve supply from the accessory nerve, and whose action turns the head obliquely to the opposite side and flexes the neck and extends the head when both sides act together.sternomastoid
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.